How to identitfy which field has been selected

When using a Simple On-Click is it possible to identify on which field the regex has been matched ? An example is within the Address Book when one hovers over the work fax field are we able to capture that field name and check against it ? I would like to be able to provide a simple click that when a user hovers over the number for the fax it will popup and say Click to Send Fax. This would then up a email compose window with the To: and Subject pre-filled. The To: field will be populated from a user preference stored in Zimbra.